The website I am working on uses getimagesize to rescale images.
We're setting up a new site using the same images, but am having trouble getting the image size. I think its because of the images being in a different document root to the script, though it displays the image fine.

When dealing with paths in PHP, you're dealing with the actual path in the operating system, not the path from the web server's document root. So if the file is in some other document root, use the absolute path to that document root on the filesystem (hint: an absolute path always starts with /).